Fixing the final toner image with heat is widely standard in electrophotographic apparatus. In this invention, heating is at two stages, one immediately prior to final fixing and one being final fixing in which the paper is pressed between an intermediate member carrying the image as toner particles and a heated roller. In this invention the surface of the paper which will receive the toner is directly heated in the first stage.
U.S. Pat. No. 3,851,964 to Smith et al employs hot air manifolds to heat the final paper prior to transfer of the image directly from the photoconductor surface. At the location of image transfer the paper passes around a roller termed a printing roller and is directed under another heating manifold. Preheating particularly improves results for liquid toner systems. The toner in this patent is liquid, as is the preferred toner in this application.
U.S. Pat. No. 4,755,849 to Tarumi at al discloses embodiments of an electrophotographic imaging system having an intermediate image transfer member, transfer and fixing with heat and by contact between the transfer member and an opposing roller, and preheating of the final paper directly with a heated plate contacting the side receiving the image. Except for the FIG. 5 embodiment, the heated plate is part of a guide path in which the paper is bent. In the FIG. 5 embodiment the intermediate transfer member is not employed, but the plate contacts the paper on the side opposite the image.
U.S. Pat. No. 4,455,079 to Miwa et al discloses a preheating member on the print-receiving side of the paper curved around a pressure roller. Similarly, U.S. Pat. No. 4,518,976 to Tarumi et al discloses a preheating member on the print-receiving side of the paper curved around the pressure roller as well at least one other embodiment (FIG. 10) in which the heating is to the opposite side.